lets clarify this a little so some dont get confused .the tv plunger comes with the white spring ,not the tv valve .the tv valve is in front of the second rol pin in the plungers bore .i always use the stock spring UNLESS I FIND THAT THE PLUNGER MOVES BEFORE IT CONTACTS THE SPRING .this is unacceptable and should be corrected during rebuilds or servicing .herw is why .the plunger is fed 90 psi of oil .this 90 psi at the plunger is now reregulated to between 0 and 90 psi leaving the plunger to reregulate line pressure at the tv boost valve in the pump .now ,as we know the throttle blades of the throttle body rotate between 0 degrees when closed and 90 degrees at wide open throttle we can understand that for every degree of throttle opening there should also be a corresponding 1 psi in oil pressure entering the modified tv oil circuit where it now controls the pressure regulator system between 90 and 245 psi (roughly )after passing through the line bias valve .also controls tv up and down oil. as you can see it does have a big influence on trans operation. A WEAK SPRING CAN DELAY LINE RISE BY NOT PUSHING ON THE TV VALVE CAUSING NO MODULATED BOOST OIL TO CONTROL PUMP MAINLINE PRESSURE RESULTING IN REDUCED CLUTCH CLAMPING FORCE AT UP TO 25 DEGREES OF THROTTLE OPENING .now if the spring is too long it can cause the vehicle to shift late at lite throttle and also cause rough engagements from park to drive or park to reverse . extreme cases can experience a myriad of kickdown over aggressiveness as well as other crap . the plunger should have .001 of an inch clearance between it and the spring .